This invention relates to a clutch-actuating device and a coupling to be used therein for a vehicle whose transmission is shifted by manual operation.
In a motor vehicle whose transmission is manually operated, a driver performs a series of operating steps including pressing down on a clutch pedal to temporarily disengage the transmission from an engine when shifting gears, changing the gear ratio by manipulating a gearshift lever, and reengaging the transmission with the engine by releasing the clutch pedal. If the clutch pedal is not properly released in this flow of the operating steps, occasionally the body of the vehicle may rock or the engine may stop due to so-called torque shocks caused by the clutch.
To overcome this problem, Japanese Unexamined Patent Publication No. 4-145236, for instance, proposes an arrangement involving the provision of a torque shock protection valve in the middle of a conduit for supplying hydraulic fluid from a master cylinder to an operating cylinder, in which the flow rate of hydraulic fluid returning from the operating cylinder to the master cylinder as a result of clutch release action is limited to prevent the occurrence of torque shocks. This torque shock protection valve is fixed to the vehicle body by means of a bracket.
The aforementioned arrangement employing the torque shock protection valve, which is constructed as an component separate from either the master cylinder or the operating cylinder, has a problem that man-hours requirements for assembly increase due to the need for fixing the valve to the vehicle body. Contrary to this, if the torque shock protection valve is shipped preassembled in a clutch-actuating device, it is difficult to maintain the torque shock protection valve unfixed to the vehicle body in a stable state during transportation.
Under such circumstances, a clutch-actuating device disclosed in Japanese Examined Patent Publication No. 2-76230, for instance, overcomes the aforementioned problems occurring at the time of assembly and during transportation by incorporating a valve element having a restriction aperture which serves as a torque shock protection valve in an operating cylinder illustrated in FIG. 2.
The torque shock protection valve may, however, be installed or not installed on a motor vehicle depending on engine displacement, for example. Therefore, if the torque shock protection valve is incorporated in the operating cylinder by machining its conduit connecting block as is the case with the aforementioned clutch-actuating device of Japanese Examined Patent Publication No. 2-76230, this operating cylinder can only be used in a motor vehicle designed to be equipped with a torque shock protection valve. Then, a problem arises that it is necessary to prepare another type of operating cylinder for motor vehicles not requiring a torque shock protection valve.
The aforementioned clutch-actuating device in which the torque shock protection valve is factory-incorporated in a specific cylinder (or in the operating cylinder) has a further problem that it spoils flexibility in the design of hydraulic circuit layout.
It is an object of the present invention to provide a clutch-actuating device, coupling, and conduit unit which are free from the problems residing in the prior art.
According to an aspect of the invention, a clutch-actuating device is provided with a master cylinder to be actuated by depression of a clutch pedal, an operating cylinder to be actuated by fluid pressure fed from the master cylinder through a conduit which is connected to the master cylinder or the operating cylinder via a coupling member, and a restriction mechanism for restricting the flow of hydraulic fluid returning from the operating cylinder to the master cylinder, the restriction mechanism being incorporated in the coupling member.
According to another aspect of the invention, a coupling having a restriction mechanism for a clutch-actuating device, the coupling being provided with a cylindrical member having a cylinder-connecting part to be connected to a port of a master cylinder or an operating cylinder at one end, and a conduit-connecting part to be connected to a conduit at the other end. The restriction mechanism restricts the flow of hydraulic fluid returning from the operating cylinder to the master cylinder, and is incorporated in a through hole formed in the cylindrical member.
According to still another aspect of the invention, a conduit unit for a clutch-actuating device is constructed by: the above-defined coupling, a coupling having a cylinder-connecting part to be connected to a port of a master cylinder or an operating cylinder at one end and a conduit-connecting part to be connected to a conduit at the other end, and a conduit for connecting the coupling having the restriction mechanism to the coupling.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments/examples with reference to the accompanying drawings.